Metal-treating apparatus and process



July 7, 192s. Y l l1,545,305

F. M. CRAPO ET AL METAL TREATING APPARATUS AND PROCESS mVENToRs marisa .hay 7, 1925.

IJNITD srurlazsl PATEN'II, OFFICE.

rannnarcx n. amro 'AND WILLnut BAYLIS, vor xUN'cm, INDIANA.

' IETAL-TBEATING APPARATUS AND PROCESS.

applicati@ mea ApriI 21, 1924. serial No. 707,869.

Treating Apparatus and Process, of which` the following is a' specification.l

Our invention relates to an improved process and apparatus for chemically heattreating iron and Steel articles, especially wire or rod. More specifically, this process and apparatus is for use in making the protected-metal set forth in the lco-pending application of Frederick M. Crapo, Serial No. 679,650, filed 'December 10, 1923, now yPatent No. 1,501,887', granted July 15, 1924.

According to such prior application, considered .very briefly and very specifically, iron or low-carbon steel wire which is subsequently to be zinc-coated is chemically heat-treated by being passed through a bathv ofl molten surface-hardening treating material in which the chemical heat-treatment is effected. By such chemical heat-treatment, there is produced in the wire a permeat-ive addition by chemical change anda heattreatment;and in the specific process there set forth these include annealing and surface hardening. The treatingV materia used with best successcontainedcarbonizing material, such as commercial cyanide mixtures.

It is found, however, that the molten salts containing cyanide adversely affect any ordinary container therefor, and make the life of such container very short; and also that a considerable volume of such molten salts must be used, that, there is a considerable loss of salts in` operation, andf that replenishment of the salt bath must be made with a salt mixture of rather high c anide contellit, when the container direct y holds the sa ts.

-It is vthe fundamental object of our present invention to reduce or eliminate this injurious effect on. the container, to reduce this volume of salts, to reduce the loss of sa ts, the salt bath with a salt mix-ture o lower cyanide content.

In carrying outour invention, we float the surface-'hardenin treating-material to be 'used in the chemical heat-treatment on a heavier molten material, conveniently l through the and to make it possible to re lenish lead, which lead in turn is carried in the container. The treating material is confined to a definite part of the surface of the heavier molten vmaterial, by a suitable circnmscribing band or ring supported so that its walls extend both above and below such surface. Thus the treating material is kept from contact Withthe container, and ad- -verse effects thereof on -the container proper are eliminated. The band itself may be adversely affected by but this effect on the band is much less harmful because the band is not subjected to the flames as the container is, and in any case the band can be replaced at relatively small cost, inconvenience, and delay, as compared with the container.v i

The articles to be treated, such as the `iron or steel wire,.are chemically treated in the treating material in the band. This treating material conveniently consists of molten salts, and we find lcommercial cyanide mixtures to be very advantageous. This treatment is most conveniently obtained, with economy in the use of salts, if the wire is first passed into the molten lead at a point outside of the band, and'carried along beneath the surface of the molten lead to'a point beneath the band, then passed upward molten salts, and thence carried desired 'subsequent treatments. While passing through the molten lead, the wire is heated so that the time it need remain in the salts' may be even shorter than that contemplated in the aforesaid Crapo, application. The wire is well annealed as it leaves the molten salts; and, further, carto any ries with it a slight film of such salts, whichv f ilm probably continues its action on the surface of the wire for an ap reciabletime as the wire cools and in addition prevents oxidation of the surface of the wire. This whole operation is continuous in the case of wire and rods.

After' this chemical heat-treatment, the wire may be passed through or baths, such as a water bath to remove the adhering salts and a fluxingY bath; andthen is zinc-coated, as by being assed through a bath of molten zinc, if t at is desirable. This zinc coating is of the superior quality of the Crapo product set forth in the aforesaid prior application. Y i

The accompanying drawing illustrates our invention: Fig. 1 is a longitudinal sectional a suitable bath I the treatingmaterial,

view showing diagrammatically an appational view showing diagrammatically an apparatus embodying our invention as used for chemically 'heat-treating rods before drawing, or wire 'at an intermediate stage of drawing; Fig. 3 is an enlarged transverse section on the line 3 3 of Figs. 1 and 2; and Fig. 4 is a fragmental -plan showing the salt-confining band.

The iron-vasewire 10 is presumed to have been passed previously through the `desired sizing dies, until it.' has reached the gage at which it is desired to zinc-coat it. Then it is passed into a container 11, containing molten lead 12; the lead being maintained molten by a suitable lire 13 beneath such container. The wire is' passed for some distance through the lead, beneath its surface, and is then passed up through a bath of molten salts 14 floated on top of the molten lead and heated therefrom.` The salts- 14 may also be heated from above, as by an .auxiliary gas burner15; but the lead is desirably maintained at higher temperature than the salts, so that wire or rod entering the salts from below will be hotter than such salts. The salts are confined to a definite part of the surface of the lead by a circumscribing band or ring 16. rlhe wire after it leaveslthe molten salts is passed through any suitable baths, of which we have shown a bath 17 of Water for removing any adhering salts and a bath 18 of a snitable lux such as hydrochloric acidor zinc chloride; then if desired over a hot plate ments which it ma 19 to insure drying of the wire; and then througha bath 20 of molten zinc in which the wlre takes its zinc coating. From the zinc-coating bath 20, of molten zinc, the wire i passes to the winding reel 21. All this is in Y a continuous process, with the wire moving continuously inthe direction of the arrows. The intermediate baths shown, such as the water bath 17 and the fluxing bath 18, are merely to exemplify any intermediate treatbe desired to give the wire, and are not limitations onY what such treatments may be. Further, the ,zinc-coating may be applied inA various ways; althou h the way we prefer to apply it, especia ly to wire, is by passing the wire through a bath 'ofmolten zinc.. Such zinccoating bath is advantageously maintained at about 840 to 900o F., in any convenient way, rthou h that temperature may be varied in the juggment'of the operator.

The band or ring 16 may be of any desired size and shape, to permit any desired number vof wires to pass through it, and may and are bolted to the sides of the container '11. The walls of the band 16 project downward slightly into the molten lead, and upward above the upper surface of the molten salts contained within it. These salts are maintained at a temperature somewhat above their melting point, advantageously between 1200 and 1350" F., by heat from the bath of molten lead below, and from the auxiliary burner 15 if that -is used, and from the wires passing through the salts.

The lead is desirably maintained between 1275o to 1375 F. It is usually desirable y* that the lead be covered with a pulverized hard coal or charcoal layer 23, which serves both to prevent heat loss by radiation and to lessen oxidation of the lead. For carry-v ing off fumes, a hood 24 may be provided over the bath 11. The passage of the Wire through the bath 11` is guided` by.suitable sinkers 25 and 26, of which the latter may conveniently be formed on a lower edge of the band 16, as shown in Figs. 1 and 2, although as shownin Fig. 4 the band 16 may be made without having such sinker 26 formed thereon. The band 16 is desirably` covered by removable cover plates 27, to lessen cooling of the salts. A pin-board Wipe 28 is desirably provided for the wires as they emerge from the salts. Thisv pinboard wipe comprises a cross-bar over which the wires slide, and a series of pinsvprojecting from said cross-bar between said wires to keep them separated. Y

The Wire as it passes through the molten lead and the molten salts is given the desired chemical heat-treatment. The wire is annealed and pre-heated in its passage v ythrough themolten lead. Then, as the wire passes up from the molten lead into and through the molten salts, it receives a surface-hardening treatment. The salts we prefer to use contain some cyanide, and we find that a cyanide ,mixture containing one part sodium cyanide, two parts sodium chloride, and four parts sodium carbonate produces good results. This produces on the wire a very thin surface change, probably involving carbonization and other things; and in addition the wire as' it p-asses through the lead and through the salts is thoroughly and effectively annealed.

Referring now to the apparatus shown in salts 14, and circumscribing band 16 are substantially the same as -illustrated in Fig. 1. The wire o'r rod 10',- however, is assumed not to have reached the final gage, and may be merely the rod before therehas been any drawing operation. Such rod as it passes through the lead and salts is chemically heattreated. After' the rod or wire 10 passes v from the molten salts, it may pass through a suitable water bath 17, to remove any adof salts in operation,

v without any -container by the salts.

and may thenfbe wound on a hering salts,

21 ready for subsequent draw winding reel ing.

The amount of salts .-necessa with `the band 16 is very muchless than is necessary` if such salts comprise the entire contents of the container 11. This reduces the loss y largely because of the reduction in exposed area of such salts. Moreover, because uof this reduction in loss of. salts andl because of the relativel small volume of salts, replenishment of't e salts may be made with cyanide mixtures having lower cyanide content, as the quantities used in replenishing are much lar er fractions of the whole. Further, the d'16 holds the salts away from the container 11, -so that there is noeffect produced on such 'This increases the life of the container many times. The c ect of the salts on the band 16 is not of.

t' moment; not only because such band is not ex sed tothe flame, but also because if t e ,salts in any case do adversely affect the band the latter may be replaced easily and cheaply, which m-ay be done loss of-materialg and vfwithout-i any danger such as occurs from the burning out of a container, and without the labor which is necessary to set a new container in place inits foundations.

We 'claim as our invention 1. In an apparatus for chemically heattreating metal articles, the vcombination of a container holding molten material, a surmaterial floating said molten maband for Icon face-hardening treating on part of the surface of terial, and a circumscribing lining said treating materia to part of said surface and preventing itA from. coming in contact with said container.

2. The combination set forth in claim 1, with the addition that said treating material contains cyanide.

3. The combination set forth in claim 1, with the addition of means for heating said. treating material from above.v 4. The combination set forth in claim 1,

with the addition that said molten material is lead.

5. The -combination set forth in claim 1 with the addition that said molten materia is lead, and,l that said treating material .contains cyanide.

6. The combination set forth inl claim 1, with ythe addition that said treating' material is in a molten state but at a lower temperawith the addition of means for ture than that of the body of molten material on which it floa 7 The combination set forth in claim 1, with the addition of means for conducting a wire or rodv through said two materials in series.

8. The combination1v set forth m-cla1m 1,

conducting a sois.V

wire or rod into-said molten material outside of said band and then vthrough the treat'lg materialfinside of said band.

9. e combination set forth in claim 1, with the addition of means for passing a wire or rod down .into and then up out of said molten material, one of said passings being vinside of and one outside of said band.

v 10. The combination set forth claim 1, with the addition of means for`passing a wire or rod down into and then up out of said molten material, one of said passings being inside of said band.

11. The combination-set forthin claim 1, -with the addition of means for passing a wire orrod'through the treating material within said band.

12. The combination set forth in claim 1, l

'with the addition of means for supporting said band from said container.

13. The process of chemically heat-treating iron or steel articles, comprising iioat- .ing a surface-hardening treating material on the surface of a bath of molten material in a container, coninin such treating material to part, of suchrgsur ace ,and outof contact with thecontainer, and 4passing such articles through s aid treatingl material.

'14. The process of chemically heat-treating iron or ing a surface-hardening treating material on the surface of a bath of molten material in a container, coninin such treating material to art of such sur aceand out of contact wit the container, through said treating material and 4said molten material in series.-

ath of and passing such articles steelv articles, comprising iloattreatconfining he continuous process of chemically wire or rod, coming 'material on the surface of a bath of` molten material in Aa container, confining such treating materialto art of such surface and out of contact with the container,

and continuously passing such wire or rod through said treating material and said molten material in series.

17. The process of chemically heat-treating iron or steel articles, comprising {loating a surface-hardening treating material on the surface of a bath of molten lead in a container, confining such treating material to. a part of such surface and'out of contact with the container, and passin 'such articles through said treating materia 18. The process of chemically heat-treatingiron or steel articles, comprising floating a surface-hardening treating material containing cyanide on 4the surface of a bath of molten material in a container, confining such treating material to part of such sur-l vface and out of contact with the container, and passing such articles through said treating material. 19. The processhof chemically heat-treat ing iron or steel articles, comprising ioating a surface-hardening tre-ating material containing cyanide on the surface of a bath of molten lead in a container, confining such treating material to part of such surface and out of contact With the container, and passing such articles 'through said treating material.

20. The processof-'chemically heat-treating iron or steel articles, comprising oating a surface-hardening treating material on thesurface of a bath of molten material in a container, confining such treating material to part of such surface, and passing such articles through said treating material.

21. In an apparatus lfor chemically heattreating metal articles, the combination of a container holding molten material, a surface-hardening treating material fioating on part of the surface of said molten material, and means for confining said treating material to part of said surface.

Inwitness whereof, We have hereunto set our hands at Muncie, Indiana, this th day of April, A. D. one thousand nine hundred and twenty-four.

FREDERICK M. CRAPO. WILLIAM BAYLIS. 

